1. Field of the Invention
The invention relates to optical sensors. More particularly, the invention relates to optical sensors formed from an optical waveguide with a large outer transverse diameter and a substantially D-shaped portion.
2. Description of the Related Art
Various industries and applications utilize optical sensors to measure parameters such as temperatures, pressures, and chemicals in a particular environment. In particular, optical sensors are finding increased applications in civil, industrial, and military fields where enhanced sensitivity, geometrical flexibility, miniaturization, immunity from electromagnetic interference and multiplexing capabilities are desirable. Optical sensors used to detect environmental parameters often require specialized structures in and around an optical fiber and tools to make the specialized structures. Additionally, some sensors are better suited in certain applications than others based on the size, accuracy, or durability of the sensor in a harsh environment with high temperatures and/or pressures.
Optical fibers having non-circular cross-sectional outer shapes such as D-shapes are used for various purposes including coupling light or the evanescent field into and/or out of the fiber and/or mechanically determining, orienting or aligning the polarization states of a fiber. When a portion of a cladding of an optical fiber is removed to create a D-shaped fiber portion, the fiber becomes fragile due to the small diameter of the cladding, e.g., about 125 microns. The fiber with the D-shape is highly lossy, difficult to manufacture and difficult to use because the fiber is delicate and fragile.
Therefore, there exists a need for an optical sensor that is durable, easy to use and easy to manufacture.